The current invention is in the field of the satellite navigational system.
In the available art relating to the satellite positional systems (SATPS), the curvature of terrain is not taken into account.
Indeed, the SATPS provides the 3-D location of signal reception (for instance, the 3-D location of the antenna). However, the position of interest is often not the same as where the satellite receiver (SR) is located since the SR is placed in the location for good signal reception. For example, for a tractor towing an implement, the best location for the SR may be on top of the tractor cab, but the position of interest (POI) for providing guidance to the tractor operator may be the position on the ground below the operator. If the tractor is on a flat terrain, determining this POI is a simple adjustment to account for the antenna height. However, if the tractor is on an inclined terrain with a variable tilt, which is often the case, the SATPS alone cannot determine the terrain tilt so the POI also cannot be determined. This results in a guidance error because the POI is approximated by the point of reception (POR), and this approximation worsens as the terrain inclination increases. By measuring tilt of vehicle with inexpensive tilt sensors, the POI can be determined, and the guidance error caused by the tilt of the terrain can be reduced.
In addition, in the prior art satellite guided parallel swathing for precision farming, the actual curvature of terrain is also not taken into account. This results in a less than precise farming because of the less than precise parallel swathing. Indeed, in order to provide parallel swaths through a field, the guidance system collects positions of the vehicle as it moves across the field. When the vehicle turns around at the end of the field and commences the next pass through the field, the guidance system sets the collected positions for the previous pass by the width of the complement (i.e. swath width). If only 3-D coordinates are collected, the next swath computations should assume a flat terrain offset. This set of next swath positions is used to provide guidance to the operator as he drives vehicle through the field. The current vehicle location as compared to the desired swath location is provided to the driver. However, if the terrain is inclined, the horizontal swath offset is in error because it does not take into consideration the curvature of the terrain. On inclined terrain, this error can be minimized by collecting vehicle tilt configuration along each current pass or the previous pass. The swath offset thus becomes a vector taking the terrain inclination into account with the assumption that from the first swath to the next one the terrain inclination does not change too much.
To meet the challenge of taking into account the actual terrain curvature, a satellite navigational system integrated with a tilt measurement system is needed. The integrated system should be capable of precise tilt measurements of the mobile unit that moves along a variable tilt track, so that the actual curvature of terrain is included in the swath vector.
To address the shortcomings of the available art, the present invention provides a method of using a satellite navigational system integrated with a tilt measurement system in order to guide a vehicle in adjacent swaths across terrain that may slope.
The present invention is directed to a method of guiding a vehicle in adjacent swaths across terrain that may slope. In one embodiment, the method comprises the following steps: (1) determining the tilt of the vehicle with respect to Earth due to a slope of the terrain; (2) determining the position with respect to Earth of a predetermined location that is fixed relative to the vehicle; and (3) using the tilt and position determinations to provide information for guiding the vehicle to prevent gaps and overlaps between adjacent swaths as the slope changes.
In one embodiment of the present invention, the step of determining the position with respect to Earth of a predetermined location further comprises the step of using the tilt and position determinations. In one embodiment, the predetermined location is at ground level.
In one embodiment of the present invention, wherein the vehicle includes a portion that is displaced from the predetermined locations and whose position with respect to the vehicle is known, the step (2) of determining the position with respect to Earth of the predetermined location further comprises the steps of: (2,1) determining the position of the displaced portion with respect to Earth; and (2,2) performing a calculation involving the tilt of the vehicle and the position of the displaced portion with respect to both Earth and the vehicle.
In one embodiment of the present invention, the position is measured with respect to x and y coordinates axes that are horizontal and a z coordinate axis that is vertical.